<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <!-- node.removeChild()方法从DOM中删除一个子节点 并返回删除的节点 -->
    <button>删除</button>
    <ul>
        <li>熊大</li>
        <li>熊二</li>
        <li>光头强</li>
    </ul>
    <script>
        var btn = document.querySelector('button');
        var ul = document.querySelector('ul');
        btn.onclick = function () {
            if(ul.children.length==0) this.disabled = true;
            else ul.removeChild(ul.children[0]);
        }
    </script>
</body>

</html>